Node device used in network system for performing packet communications, network system using the same, and communication method used in the system

Abstract

A node device that is used in a network system has a packet processing circuit, a buffer for temporarily storing a packet and a selector for selecting a channel to which the buffer is to be connected. The selector can select either a first channel connected to another node device or a second channel connected to the packet processing circuit. The buffer can store a number of packets, and of these packets the one that is addressed to the packet processing circuit is read out when the buffer is connected to the second channel.

What is claimed is: 
     
       1. A network system which is constituted by a plurality of node devices and a transmission path for connecting the node devices, and performs a communication using a packet, comprising: a transmission path for connecting the node devices; and   a node device including: packet processing means for processing a packet applied to an input of said racket processing means;   a buffer having an input coupled to an output of said packet processing means, said buffer for temporarily storing the packet;   selection means for selecting a channel, to which an output of said buffer is connected, from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer to read out from said buffer a packet using the selected channel,     wherein the plurality of channels include a first channel connected to another node device via said transmission path, and a second channel connected to said packet processing means in the node device, and wherein a packet to be output to said packet processing means in the node device is read out from said buffer when said buffer is connected to the second channel.   
     
     
       2. A system according to claim 1, wherein the second channel is input to another node device via said transmission path, is looped back by said other node device, is input to the node device, and is connected to said packet processing means. 
     
     
       3. A system according to claim 1, wherein said selection means sequentially changes the channel to be selected. 
     
     
       4. A system according to claim 1, wherein said node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects the channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       5. A system according to claim 4, wherein said selection means comprises a plurality of variable channel transmission means arranged in correspondence with said plurality of buffers. 
     
     
       6. A system according to claim 5, wherein said node device comprises means for multiplexing outputs from said plurality of variable channel transmission means and extracting an output corresponding to the second channel from the multiplexed output. 
     
     
       7. A system according to claim 4, wherein said selection means comprises connection alteration means which has input terminals respectively corresponding to said plurality of buffers and output terminals respectively corresponding to the plurality of channels, and can change a connection relationship between the input and output terminals. 
     
     
       8. A system according to claim 1, wherein said buffer receives a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, or a packet transmitted from said packet processing means. 
     
     
       9. A system according to claim 1, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device and a packet transmitted from another node device, and for inputting the selected packet to said buffer. 
     
     
       10. A system according to claim 1, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, and a packet transmitted from said packet processing means, and for inputting the selected packet to said buffer. 
     
     
       11. A system according to claim 1, wherein said node device comprises separation means for separating to a sub transmission path side a packet to be output onto a sub transmission path connected to the node device from packets input from another node device. 
     
     
       12. A system according to claim 1, wherein said node device comprises separation means for separating to a sub transmission path side a packet to be output onto a sub transmission path connected to the node device from packets transmitted using the second channel. 
     
     
       13. A system according to claim 1, wherein said transmission path transmits a packet in a first direction, and a second direction opposite to the first direction, and said node device comprises at least two buffers equivalent to said buffer, one of said buffers is a first buffer with which the first channel connected is connected to another node device at a downstream side in the first direction, and the other buffer is a second buffer with which the first channel connected is connected to another node device at a downstream side in the second direction, and further comprises, as said selection means, first selection means corresponding to said first buffer and second selection means corresponding to said second buffer.   
     
     
       14. A system according to claim 13, wherein said node device further comprises third and fourth buffers, said third buffer temporarily stores a packet to be output to another node device of packets output from said first buffer using the second channel, a channel to which said third buffer is connected is selected by said second selection means, said second selection means selects channels to which said second and third buffers are connected, so that said second and third buffers are simultaneously connected to different channels, said fourth buffer temporarily stores a packet to be output to another node device of packets output from said second buffer using the second channel, a channel to which said fourth buffer is connected is selected by said first selection means, and said first selection means selects channels to which said first and fourth buffers are connected, so that said first and fourth buffers are simultaneously connected to different channels. 
     
     
       15. A system according to claim 13, wherein said node device comprises a plurality of first buffers equivalent to said first buffer, and a plurality of second buffers equivalent to said second buffer. 
     
     
       16. A system according to claim 15, wherein said first selection means selects channels to which said plurality of first buffers are connected so that said plurality of first buffers are simultaneously connected to different channels, and said second selection means selects channels to which said plurality of second buffers are connected so that said plurality of second buffers are simultaneously connected to different channels. 
     
     
       17. A system according to claim 1, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       18. A system according to claim 1, wherein the plurality of node devices are connected in a ring pattern via said transmission path. 
     
     
       19. A network system which is constituted by a plurality of node devices and a transmission path for connecting the node devices, and performs a communication using a packet, comprising: a transmission path for connecting the node devices;   a first node device including: a buffer for temporarily storing the packet in response to the packet being applied to an input of said buffer;   selection means for selecting a channel to which an output of said buffer is connected from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer to read out from said buffer a packet using the selected channel; and     a second node device including: packet processing means for processing a packet,     wherein the plurality of channels include a first channel connected to said second node device via said transmission path, the first channel further being connected to a sub transmission path connected to one of said second node device and another node device via said second node device, the plurality of channels further including a second channel connected via said transmission path to said packet processing means in said second node device, and wherein a packet to be output to said packet processing means in said second node device is read out from said buffer when said buffer is connected to the second channel.   
     
     
       20. A system according to claim 19, wherein said selection means sequentially changes the channel to be selected. 
     
     
       21. A system according to claim 19, wherein said first node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       22. A system according to claim 21, wherein said selection means comprises a plurality of variable channel transmission means arranged in correspondence with said plurality of buffers. 
     
     
       23. A system according to claim 19, wherein said second node device comprises means for extracting the second channel from the plurality of channels transmitted from said first node device via said transmission path. 
     
     
       24. A system according to claim 21, wherein said selection means comprises connection alteration means which has input terminals respectively corresponding to said plurality of buffers and output terminals respectively corresponding to the plurality of channels, and can change a connection relationship between the input and output terminals. 
     
     
       25. A system according to claim 19, wherein said buffer receives one of a packet transmitted from a sub transmission path connected to said first node device, a packet transmitted from another node device, and a packet transmitted from said packet processing means. 
     
     
       26. A system according to claim 19, wherein said first node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to said first node device and a packet transmitted from another node device, and inputting the selected packet to said buffer. 
     
     
       27. A system according to claim 19, wherein said first node device further comprises packet processing means, and insertion means for selecting one of a packet transmitted from a sub transmission path connected to said first node device, a packet transmitted from another node device, and a packet transmitted from said packet processing means of said first node device, and inputting the selected packet to said buffer. 
     
     
       28. A system according to claim 19, wherein said first node device comprises separation means for separating a packet to be output onto a sub transmission path connected to said first node device from packets input from another node device as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       29. A system according to claim 19, wherein said second node device comprises separation means for separating a packet to be output onto a sub transmission path connected to said second node device from packets input from another node device as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       30. A system according to claim 19, wherein said transmission path transmits a packet in a first direction, and a second direction opposite to the first direction, and said first node device comprises at least two buffers equivalent to said buffer, one of said buffers is a first buffer with which the first channel connected is connected to said second node device at a downstream side in the first direction, and the other buffer is a second buffer with which the first channel connected is connected to said second node device at a downstream side in the second direction, and further comprises, as said selection means, first selection means corresponding to said first buffer and second. selection means corresponding to said second buffer.   
     
     
       31. A system according to claim 30, wherein said first node device further comprises third and fourth buffers, said third buffer temporarily stores a packet to be output to another node device of packets output from said first buffer using the second channel, a channel to which said third buffer is connected is selected by said second selection means, said second selection means selects channels to which said second and third buffers are connected, so that said second and third buffers are simultaneously connected to different channels, said fourth buffer temporarily stores a packet to be output to another node device of packets output from said second buffer using the second channel, a channel to which said fourth buffer is connected is selected by said first selection means, and said first selection means selects channels to which said first and fourth buffers are connected, so that said first and fourth buffers are simultaneously connected to different channels. 
     
     
       32. A system according to claim 30, wherein said first node device comprises a plurality of first buffers equivalent to said first buffer, and a plurality of second buffers equivalent to said second buffer. 
     
     
       33. A system according to claim 32, wherein said first selection means selects channels to which said plurality of first buffers are connected so that said plurality of first buffers are simultaneously connected to different channels, and said second selection means selects channels to which said plurality of second buffers are connected so that said plurality of second buffers are simultaneously connected to different channels. 
     
     
       34. A system according to claim 19, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       35. A system according to claim 19, wherein the plurality of node devices including said first and second node devices are connected in a ring pattern via said transmission path. 
     
     
       36. A communication method in a network system which is constituted by a plurality of node devices and a transmission path for connecting the node devices, and performs a communication using a packet, comprising: a transmission path for connecting the node devices; and   a node device including: packet processing means for processing a packet applied to an input of said packet processing means;   a buffer having an input coupled to an output of said packet processing means, said buffer for temporarily storing the packet;   selection means for selecting a channel to which an output of said buffer is connected, from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer to read out from said buffer a packet using the selected channel,     said method comprising the steps of:   selecting a second channel by said selection means, the plurality of channels including a first channel connected to another node device via said transmission path, and the second channel connected to said packet processing means in the node device; and   controlling said buffer by said buffer control means to read out a packet to be output to said packet processing means in the node device and stored in said buffer while said selection means selects the second channel.   
     
     
       37. A method according to claim 36, wherein said selection means sequentially changes the channel to be selected. 
     
     
       38. A method according to claim 36, wherein said node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects the channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       39. A method according to claim 36, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       40. A method according to claim 39, wherein a terminal equipment is connected to said node device via a sub transmission path, and the management packet includes a packet used by said terminal equipment for inquiring of address information of another terminal equipment, or a packet for responding to the inquiry packet. 
     
     
       41. A method according to claim 39, wherein the management packet is a packet for managing a connection between the node devices. 
     
     
       42. A method according to claim 36, wherein the packet has relaying number information indicating the number of times the packet is relayed via said selection means in one or a plurality of node devices until the packet reaches a destination, and a channel to which said buffer is connected while the packet is read out is determined with reference to the relaying number information.   
     
     
       43. A method according to claim 36, wherein the packet has channel designation information indicating a channel to which a destination of the packet is connected, and a channel to which said buffer is connected while the packet is read out is determined with reference to the channel designation information.   
     
     
       44. A method according to claim 36, wherein the packet has packet kind information indicating whether said packet processing unit is an intended destination of the packet. 
     
     
       45. A method according to claim 42, wherein said node device processes the relaying number information of a packet to be output so that the number of times the packet is relayed via said selection means can be discriminated later based on the relaying number information. 
     
     
       46. A method according to claim 42, wherein the packet has channel designation information indicating a channel to which a destination of the packet is connected, and a packet in which the relaying number information indicates that the packet is to be relayed via said selection means once more is read out from said buffer while said buffer is connected to a channel indicated by the channel designation information of the packet.   
     
     
       47. A method according to claim 42, wherein a packet in which the relaying number information indicates that the packet is to be relayed via said selection means at least twice more is read out from said buffer while said buffer is connected to a channel other than the second channel. 
     
     
       48. A method according to claim 42, wherein the packet has packet kind information indicating whether said packet processing unit is an intended destination of the packet, and a packet in which the relaying number information indicates that the packet is to be relayed via said selection means once more, and the packet kind information indicates that the intended destination of the packet is said packet processing unit, is read out from said buffer while said buffer is connected to the second channel.   
     
     
       49. A communication method in a network system which is constituted by a plurality of node devices and a transmission path for connecting the node devices, and performs a communication using a packet, comprising: a transmission path for connecting the node devices;   a first node device including: a buffer for temporarily storing the packet in response to the Packet being applied to an input of said buffer;   selection means for selecting a channel to which an output of said buffer is connected, from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer to read out from said buffer a packet using the selected channel; and     a second node device including: packet processing means for processing a packet,     said method comprising the steps of:   selecting a second channel by said selection means, the plurality of channels including a first channel connected to said second node device via said transmission path, the first channel further being connected to a sub transmission path connected to one of said second node device and another node device via said second node device, the plurality of channels further including the second channel connected via said transmission path to said packet processing means in said second node device; and   reading out a packet to be output to said packet processing means in said second node device and stored in said buffer while said selection means selects the second channel.   
     
     
       50. A method according to claim 49, wherein said selection means sequentially changes the channel to be selected. 
     
     
       51. A method according to claim 49, wherein said first node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects the channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       52. A method according to claim 49, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       53. A method according to claim 52, wherein a terminal equipment is connected to said first node device via a sub transmission path, and the management packet includes a packet used by said terminal equipment for inquiring of another terminal equipment as to address information, or a packet for responding to the inquiry packet. 
     
     
       54. A method according to claim 52, wherein the management packet is a packet for managing a connection between the node devices. 
     
     
       55. A method according to claim 49, wherein the packet has relaying number information indicating the number of times the packet is relayed via said selection means in one or a plurality of node devices until the packet reaches a destination, and a channel to which said buffer is connected while the packet is read out is determined with reference to the relaying number information.   
     
     
       56. A method according to claim 49, wherein the packet has channel designation information indicating a channel to which a destination of the packet is connected, and a channel to which said buffer is connected while the packet is read out is determined with reference to the channel designation information.   
     
     
       57. A method according to claim 49, wherein the packet has packet kind information indicating whether said packet processing unit is an intended destination of the packet. 
     
     
       58. A method according to claim 55, wherein said first node device processes the relaying number information of a packet to be output so that the number of times the packet is relayed via said selection means can be discriminated later based on the relaying number information. 
     
     
       59. A method according to claim 55, wherein the packet-has channel designation information indicating a channel to which a destination of the packet is connected, and a packet in which the relaying number information indicates that the packet is to be relayed via said selection means once more is read out from said buffer while said buffer is connected to a channel indicated by the channel designation information of the packet.   
     
     
       60. A method according to claim 55, wherein a packet in which the relaying number information indicates that the packet is to be relayed via said selection means at least twice more is read out from said buffer while said buffer is connected to a channel other than the second channel. 
     
     
       61. A method according to claim 55, wherein the packet has packet kind information indicating whether said packet processing unit is an intended destination of the packet, and a packet in which the relaying number information indicates that the packet is to be relayed via said selection means once more, and the packet kind information indicates that the intended destination of the packet is said packet processing unit, is read out from said buffer while said buffer is connected to the second channel.   
     
     
       62. A node device for communicating through a transmission path, including: packet processing means for processing a packet applied to an input of said packet processing means;   a buffer having an input coupled to an output of said packet processing means, said buffer for temporarily storing the packet;   selection means for selecting a channel, to which an output of said buffer is connected, from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer for reading out a packet using the selected channel,   wherein the plurality of channels include a first channel connected to another node device via said transmission path, and a second channel connected to said packet processing means in the node device, and wherein a packet to be output to said packet processing means in the node device is read out from said buffer when said buffer is connected to the second channel.   
     
     
       63. A node device according to claim 62, wherein the second channel is input to another node device via said transmission path, is looped back by said other node device, is input to the node device, and is connected to said packet processing means. 
     
     
       64. A node device according to claim 62, wherein said selection means sequentially changes the channel to be selected. 
     
     
       65. A node device according to claim 62, wherein said node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects the channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       66. A node device according to claim 65 wherein said selection means comprises a plurality of variable channel transmission means arranged in correspondence with said plurality of buffers. 
     
     
       67. A node device according to claim 66, wherein said node device comprises means for multiplexing outputs from said plurality of variable channel transmission means and extracting an output corresponding to the second channel from the multiplexed output. 
     
     
       68. A node device according to claim 65, wherein said selection means comprises connection alteration means which has input terminals respectively corresponding to said plurality of buffers and output terminals respectively corresponding to the plurality of channels, and can change a connection relationship between the input and output terminals. 
     
     
       69. A node device according to claim 62, wherein said buffer receives a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, or a packet transmitted from said packet processing means. 
     
     
       70. A node device according to claim 62, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device and a packet transmitted from another node device, and for inputting the selected packet to said buffer. 
     
     
       71. A node device according to claim 62, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, and a packet transmitted from said packet processing means, and for inputting the selected packet to said buffer. 
     
     
       72. A node device according to claim 62, wherein said node device comprises separation means for separating a packet to be output onto a sub transmission path connected to the node device from packets input from another node device as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       73. A node device according to claim 62, wherein said node device comprises separation means for separating a packet to be output onto a sub transmission path connected to the node device from packets transmitted using the second channel as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       74. A node device according to claim 62, wherein said transmission path transmits a packet in a first direction, and a second direction opposite to the first direction, and said node device comprises at least two buffers equivalent to said buffer, one of said buffers is a first buffer with which the first channel connected is connected to another node device at a downstream side in the first direction, and the other buffer is a second buffer with which the first channel connected is connected to another node device at a downstream side in the second direction, and further comprises, as said selection means, first selection means corresponding to said first buffer and second selection means corresponding to said second buffer.   
     
     
       75. A node device according to claim 74, wherein said node device further comprises third and fourth buffers, said third buffer temporarily stores a packet output from said first buffer using the second channel, a channel to which said third buffer is connected is selected by said second selection means, said second selection means selects channels to which said second and third buffers are simultaneously connected to different channels, said fourth buffer temporarily stores a packet to be output to another node device of packets output from said second buffer using the second channel, a channel to which said fourth buffer is connected is selected by said first selection means, and said first selection means selects channels to which said first and fourth buffers are connected, so that said first and fourth buffers are simultaneously connected to different channels. 
     
     
       76. A node device according to claim 74, wherein said node device comprises a plurality of first buffers equivalent to said first buffer, and a plurality of second buffers equivalent to said second buffer. 
     
     
       77. A node device according to claim 76, wherein said first selection means selects channels to which said plurality of first buffers are connected so that said plurality of first buffers are simultaneously connected to different channels, and said second selection means selects channels to which said plurality of second buffers are connected so that said plurality of second buffers are simultaneously connected to different channels. 
     
     
       78. A node device according to claim 62, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       79. A node device according to claim 62, wherein the plurality of node devices are connected in a ring pattern via said transmission path. 
     
     
       80. A communication method using a node device for communicating through a transmission path, said node device including: packet processing means for processing a packet applied to an input of the packet processing means;   a buffer having an input coupled to an output of said packet processing means, said buffer for temporarily storing the packet;   selection means for selecting a channel, to which an output of said buffer is connected, from a plurality of different channels; and   buffer control means having an output coupled to said buffer, said buffer control means for controlling said buffer for reading out from said buffer a packet using the selected channel,   said method comprising the steps of:   selecting a second channel by said selection means, the plurality of channels including a first channel connected to another node device via said transmission path, and the second channel connected to said packet processing means in the node device; and   controlling said buffer by said buffer control means to read out a packet to be output to said packet processing means in the node device and stored in said buffer while said selection means selects the second channel.   
     
     
       81. A method according to claim 80, wherein the second channel is connected to said packet processing means in the node device. 
     
     
       82. A method according to claim 80, wherein the second channel is input to another node device via said transmission path, is looped back by said other node device, is input to the node device, and is connected to said packet processing means. 
     
     
       83. A method according to claim 81, wherein said selection means sequentially changes the channel to be selected. 
     
     
       84. A method according to claim 80, wherein said node device comprises a plurality of buffers equivalent to said buffer, and said selection means selects channels to which said plurality of buffers are connected so that said plurality of buffers are simultaneously connected to different channels. 
     
     
       85. A method according to claim 84, wherein said selection means comprises a plurality of variable channel transmission means arranged in correspondence with said plurality of buffers. 
     
     
       86. A method according to claim 85, wherein said node device comprises means for multiplexing outputs from said plurality of variable channel transmission means and extracting an output corresponding to the second channel from the multiplexed output. 
     
     
       87. A method according to claim 85, wherein said selection means comprises connection alteration means which has input terminals respectively corresponding to said plurality of buffers and output terminals respectively corresponding to the plurality of channels, and can change a connection relationship between the input and output terminals. 
     
     
       88. A method according to claim 80, wherein said buffer receives a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, or a packet transmitted from said packet processing means. 
     
     
       89. A method according to claim 80, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device and a packet transmitted from another node device, and for inputting the selected packet to said buffer. 
     
     
       90. A method according to claim 81, wherein said node device comprises insertion means for selecting one of a packet transmitted from a sub transmission path connected to the node device, a packet transmitted from another node device, and a packet transmitted from said packet processing means, and for inputting the selected packet to said buffer. 
     
     
       91. A method according to claim 80, wherein said node device comprises separation means for separating a packet to be output onto a sub transmission path connected to the node device from packets input from another node device as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       92. A method according to claim 80, wherein said node device comprises separation means for separating a packet to be output onto a sub transmission path connected to the node device from packets transmitted using the second channel as a separated packet and for outputting the separated packet to the sub transmission path. 
     
     
       93. A method according to claim 80, wherein said transmission path transmits a packet in a first direction, and a second direction opposite to the first direction, and said node device comprises at least two buffers equivalent to said buffer, one of said buffers is a first buffer with which the first channel connected is connected to another node device at a downstream side in the first direction, and the other buffer is a second buffer with which the first channel connected is connected to another node device at a downstream side in the second direction, and further comprises, as said selection means, first selection means corresponding to said first buffer and second selection means corresponding to said second buffer.   
     
     
       94. A method according to claim 93, wherein said node device further comprises third and fourth buffers, said third buffer temporarily stores a packet output from said first buffer using the second channel, a channel to which said third buffer is connected is selected by said second selection means, said second selection means selects channels to which said second and third buffers are simultaneously connected to different channels, said fourth buffer temporarily stores a packet to be output to another node device of packets output from said second buffer using the second channel, a channel to which said fourth buffer is connected is selected by said first selection means, and said first selection means selects channels to which said first and fourth buffers are connected, so that said first and fourth buffers are simultaneously connected to different channels. 
     
     
       95. A method according to claim 93, wherein said node device comprises a plurality of first buffers equivalent to said first buffer, and a plurality of second buffers equivalent to said second buffer. 
     
     
       96. A method according to claim 95, wherein said first selection means selects channels to which said plurality of first buffers are connected so that said plurality of first buffers are simultaneously connected to different channels, and said second selection means selects channels to which said plurality of second buffers are connected so that said plurality of second buffers are simultaneously connected to different channels. 
     
     
       97. A method according to claim 80, wherein said packet processing means performs processing of a management packet for communication management. 
     
     
       98. A method according to claim 80, wherein the plurality of node devices are connected in a ring pattern via said transmission path.